Field of the Invention
The invention relates to a device for driving at least one capacitive actuator, in particular an actuator of a fuel injection valve of a motor vehicle internal combustion engine. The device drives the capacitive actuator(s) by means of a control circuit. A charging capacitor is connected between the positive pole and the negative pole of a voltage source. A series circuit, connected in parallel with the charging capacitor, comprises a ring-around coil and at least one actuator with an assigned selector switch. The device further includes a discharging switch. The invention also relates to a method for operating the device.
A device of this type is disclosed in U.S. Pat. No. 4,688,536, entitled "drive circuit for an electrostrictive actuator in a fuel injection valve." There, use is made of thyristors for the charging or selector switch and a discharging switch. During the switch-on operation, thyristors must be triggered with a pulse, and are extinguished automatically when the power current flowing via them vanishes. The relatively long critical hold-off interval of the thyristors is problematical. This can be countered if the thyristors are replaced by MOSFET switches and diodes. However, a very complicated high-side drive circuit is required for N-MOSFET switches; it is certainly true that the drive circuit can be of simpler construction for P-MOSFET switches, but with these the losses are approximately twice as high as with N-MOSFET switches.